Apparatus and methods for extended base station range using staggered uplink frame structures

• US 6,633,559 B1
• Filed: 08/11/1999
• Issued: 10/14/2003
• Est. Priority Date: 08/11/1999
• Status: Expired due to Term

• Current Assignee: Optis Cellular Technology LLC (Brevet Capital)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Asokan, Ramanathan, Raith, Alex Krister
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Le, Danh C
• Application Number:
  US09/372,015
• Time in Patent Office: 1,525 Days
• Field of Search: 455/67.1, 455/561, 455/502, 455/91, 455/515, 455/449, 370/350, 370/335, 370/337, 370/252, 370/150, 370/347, 370/503
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04W 16/26 Cell enhancers or enhancement, e.g. for tunnels, building shadow
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface

Abstract

A first group of terminals at a first range from base station is instructed, e.g., by transmitted timing advance values, to time their transmissions to arrive at a base station in synchronism with a first series of frames. A second group of terminals at a second range is instructed to time their transmissions to arrive at the base station in synchronism with a second series of frames that is time-offset with respect to the first series of frames. Transmissions from the first and second groups of terminals are, received at the base station in synchronism with the respective first and second series of frames. The transmissions from respective first and second groups may be received on respective separate carrier frequencies, or may be multiplexed on a common carrier frequency. According to another aspect, first timing information is transmitted by a base station to a terminal when the terminal is in a first range, and second timing information is transmitted to the terminal when the terminal is in a second range, the first and second timing information instructing the terminal to time its transmissions to arrive at the base station synchronized with one of first or second time-offset series of frames. The ranges may overlap, and the hysteresis may be provided in instructing the terminal to synchronize its transmissions to one of the first series of frames or the second series of frames when the terminal moves between the first and second ranges. Related wireless communications apparatus is discussed.

Claims

1. A method of operating a time-division multiplexed wireless communications system, the method comprising the steps of:

instructing a first group of terminals to time their transmissions to arrive at a base station in synchronism with a first series of frames;

instructing a second group of terminals to time their transmissions to arrive at the base station in synchronism with a second series of frames that is time-offset with respect to the first series of frames; and

receiving transmissions from a terminal of the first group and from a terminal of the second group on a common carrier frequency in synchronism with respective ones of the first and second series of frames, wherein the first and second series of frames are multiplexed on the common carrier frequency.

2. A method according to claim 1:

wherein the first group of terminals is located at a first range with respect to the base station; and

wherein the second group of terminals is located at a second range with respect to the base station.

3. A method according to claim 2, wherein the second range is more distant from the base station than the first range, and wherein the second series of frames is delayed with respect to the first series of frames.

4. A method according to claim 2, wherein the first and second ranges overlap.

5. A method according to claim 1:

wherein said step of instructing a first group of terminals comprises the step of transmitting first timing information from the base station that instructs a terminal of the first group to time its transmissions to arrive at the base station in synchronism with the first series of frames; and

wherein said step of instructing a second group of terminals comprises the step of transmitting second timing information from the base station that instructs a terminal of the second group to time its transmissions to arrive at the base station in synchronism with the second series of frames.

6. A method according to claim 5:

wherein said step of transmitting first timing information comprises the step of transmitting a first timing advance value; and

wherein said step-of transmitting second timing information comprises the step of transmitting a second timing advance value.

7. A method according to claim 1, wherein cach frame of the first and second series of frames comprises at least one time slot, and wherein a beginning of a frame from the second series of frames is delayed with respect to an end of a preceding frame of the first series of frames by a time interval that is less than the duration of one time slot.

8. A method according to claim 1, wherein said step of instructing a first group of terminals and said step of instructing a second group of terminals is preceded by the steps of:

determining respective propagation delays between respective terminals and the base station; and

categorizing the terminals into the first and second groups based on the determined propagation delays.

9. A method according to claim 8, wherein said step of determining respective propagation delays comprises the steps of:

receiving random access bursts from terminals at the base station; and

determining respective propagation delays for respective terminals based on timing of the received random access bursts.

10. A method of operating a base station in a time-division multiplexed wireless communications system, the method comprising the steps of:

transmitting first timing information to a terminal when the terminal is in a first range, the first timing information instructing the terminal to time its transmissions to arrive at the base station synchronized to a first series of frames;

transmitting second timing information to the terminal when the terminal is in a second range, the second timing information instructing the terminal to time its transmissions to arrive at the base station synchronized with a second series of frames that is time-offset with respect to the first series of frames, wherein the first and second ranges overlap; and

providing hysteresis in instructing the terminal to synchronize its transmissions to one of the first series of frames or the second series of frames when the terminal moves between the first and second ranges.

11. A method according to claim 10:

wherein said step transmitting first timing information is followed by the step of receiving a transmission from the terminal in synchronism with the first series of frames on a first carrier frequency; and

wherein said step of transmitting second timing information is followed by the step of receiving a transmission from the terminal in synchronism with the second series of frames on a second carrier frequency.

12. A method according to claim 10:

wherein said step of transmitting first timing information is followed by the step of receiving a transmission from the terminal in synchronism with the first series of frames on a common carrier frequency; and

wherein said step of transmitting second timing information is followed by the step of receiving a transmission from the terminal in synchronism with the second series of frames on the common carrier frequency.

13. A method according to claim 12, wherein each frame of the first and second frame series comprises at least one time slot, and wherein a beginning of a frame from the second series of frames is delayed with respect to an end of a preceding frame of the first series of frames by a time interval that is less than the duration of one time slot.

14. A method according to claim 10, wherein the second range is more distant from the base station than the first range, and wherein the second series of frames is delayed with respect to the first series of frames.

15. A method according to claim 10:

wherein said step of transmitting second timing information comprises the step of transmitting the second timing information in response to movement of the terminal from the first range to a portion of the second range outside of the first range; and

wherein said step of transmitting second timing information is followed by the step of transmitting the first timing information to the terminal in response to movement of the terminal from the second range to a portion of the first range outside of the second range, such that hysteresis is provided when the terminal moves between the first and second ranges.

16. An apparatus in a time-division multiplexed wireless communications system, the apparatus comprising:

means for instructing a first group of terminals to time their transmissions to arrive at a base station in synchronism with a first series of frames;

means for instructing a second group of terminals to time their transmissions to arrive at the base station in synchronism with a second series of frames that is time-offset with respect to the first series of frames; and

means for receiving transmissions from a terminal of the first group and from a terminal of the second group on a common carrier frequency in synchronism with respective ones of the first and second series of frames, wherein the first and second series of frames are multiplexed on the common carrier frequency.

17. An apparatus according to claim 16:

wherein the first group of terminals is located at a first range with respect to the base station; and

wherein the second group of terminals is located at a second range with respect to the base station.

18. An apparatus according to claim 17, wherein the second range is more distant from the base station than the first range, and wherein the second series of frames is delayed with respect to the first series of frames.

19. An apparatus according to claim 17, wherein the first and second ranges overlap.

20. An apparatus according to claim 17:

wherein said means for transmitting first timing information comprises means for transmitting a first timing advance value; and

wherein said means for transmitting second timing information comprises means for transmitting a second timing advance value.

21. An apparatus according to claim 16, wherein each frame of the first and second series of frames comprises at least one time slot, and wherein a beginning of a frame from the second series of frames is delayed with respect to an end of a preceding frame of the first series of frames by a time interval that is less than the duration of one time slot.

22. An apparatus according to claim 16, further comprising:

means for determining respective propagation delays between respective terminals and the base station; and

means for categorizing the terminals into the first and second groups based on the determined propagation delays.

23. An apparatus according to claim 22, wherein said means for determining respective propagation delays comprises:

means for receiving random access bursts from terminals at the base station; and

means, responsive to said means for receiving random access bursts, for determining respective propagation delays for respective terminals based on timing of the received random access bursts.

24. An apparatus according to claim 16:

wherein said means for instructing a first group of terminals comprises means for transmitting first timing information that instructs a terminal of the first group to time its transmissions to arrive at the base station in synchronism with the first series of frames; and

wherein said means for instructing a second group of terminals comprises means for transmitting second timing information that instructs a terminal of the second group to time its transmissions to arrive at the base station in synchronism with the second series of frames.

25. A base station for a time-division multiplexed wireless communications system, the base station comprising:

means for transmitting first timing information to a terminal when the terminal is in a first range with respect to a base station , the first timing information instructing the terminal to time its transmissions to arrive at the base station synchronized to a first series of frames; and

means for transmitting second timing information to the terminal when the terminal is in a second range, the second timing information instructing the terminal to time its transmissions to arrive at the base station synchronized with a second series of frames that is time-offset with respect to the first series of frames,

wherein the first and second ranges overlap, and

wherein said means for transmitting first timing information and said means for transmitting second timing information provide hysteresis in instructing the terminal to synchronize its transmissions to one of the first series of frames or the second series of frames when the terminal moves between the first and second ranges.

26. A base station according to claim 25, further comprising:

means for receiving a transmission from the terminal in synchronism with the first series of frames on a first carrier frequency; and

means for receiving a transmission from the terminal in synchronism with the second series of frames on a second carrier frequency.

27. A base station according to claim 25, further comprising means for receiving a transmission from the terminal in synchronism with one of the first and second series of frames on a common carrier frequency.

28. A base station according to claim 27, wherein each frame of the first and second frame series comprises at least one time slot, and wherein a beginning of a frame from the second series of frames is delayed with respect to an end of a preceding frame of the first series of frames by a time interval that is less than the duration of one time slot.

29. A base station according to claim 25, wherein the second range is more distant from the base station than the first range, and wherein the second series of frames is delayed with respect to the first series of frames.

30. A base station according to claim 25:

wherein said means for transmitting second timing information comprises means for transmitting the second timing information in response to movement of the terminal from the first range to a portion of the second range outside of the first range; and

wherein said means for transmitting first timing information comprises means for transmitting the first timing information to the terminal in response to movement of the terminal from the second range to a portion of the first range outside of the second range.

31. A wireless communications apparatus, comprising:

a base station operative to transmit first timing information that instructs a first group of terminals to time their transmissions to arrive at a base station in synchronism with a first series of frames, to transmit second timing information that instructs a second group of terminals to time their transmissions to arrive at the base station in synchronism with a second series of frames that is time-offset with respect to the first series of frames, and to receive transmissions from the first and second groups of terminals in synchronism with the respective first and second series of frames,

wherein said base station is operative to transmit first timing information to a terminal when the terminal is in a first range with respect to a base station, the first timing information instructing the terminal to time its transmissions to arrive at the base station synchronized to a first series of frames, and to transmit second timing information to the terminal when the terminal is in a second range, the second timing information instructing the terminal to time its transmissions to arrive at the base station synchronized with a second series of frames that is time-offset with respect to the first series of frames,

wherein the first and second ranges overlap, and

wherein said base station provides hysteresis in instructing the terminal to synchronize its transmissions to one of the first series of frames or the second series of frames when the terminal moves between the first and second ranges.

32. An apparatus according to claim 31, wherein said base station comprises a receiver operative to receive a transmission from a terminal of the first group at the base station on a first carrier frequency in synchronism with the first series of frames and to receive a transmission from a terminal of the second group at the base station on a second carrier frequency in synchronism with the second series of frames.

33. An apparatus according to claim 31, wherein said base station comprises a receiver operative to receive transmissions from a terminal of the first group and from a terminal of the second group at the base station on a common carrier frequency in synchronism with respective ones of the first and second series of frames, wherein the first and second series of frames are multiplexed on the common carrier frequency.

34. An apparatus according to claim 31, wherein said base station comprises:

a propagation delay determiner operative to determine respective propagation delays between respective terminals and the base station; and

a timing information determiner responsive to said propagation delay determiner and operative to determine the first and second timing information based on the determined propagation delays.

35. An apparatus according to claim 34, wherein said base station further comprises a receiver operative to receive random access bursts from terminals, and wherein said propagation delay determiner is responsive to said receiver to determine respective propagation delays for respective terminals based on timing of the received random access bursts.

36. An apparatus according to claim 31, wherein the second range is more distant from the base station than the first range, and wherein the second series of frames is delayed with respect to the first series of frames.

37. An apparatus according to claim 31, wherein said base station is operative to transmit a timing advance value to a terminal based on whether the terminal is in the first group of the second group.

38. A base station according to claim 31, wherein the base station transmits the second timing information in response to movement of the terminal from the first range to a portion of the second range outside of the first range, and wherein said base station transmits the first timing information in response to movement of the terminal from the second range to a portion of the first range outside of the second range.